Method and Apparatus for Improving a Mobile Station Cell Change Operation in the General Packet Radio System (GPRS)

ABSTRACT

A mobile station executed method, wherein upon changing from a current cell to a new cell in a wireless packet data network the mobile station enters the new cell; generates a cell change packet data unit (PDU) message for informing the network of the location of the mobile station in the new cell; buffers the cell change PDU message into a PDU transmit queue before any buffered PDUs that were present before the mobile station entered the new cell; and transmits the buffered cell change PDU before any of the buffered PDUs that were present before the mobile station entered the new cell.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/290,844 filed Nov. 3, 2008 which is a continuation of U.S.application Ser. No. 10/004,723 filed Dec. 5, 2001, now U.S. Pat. No.7,447,181, both of which are hereby incorporated by reference in theirentireties.

TECHNICAL FIELD

These teachings relate generally to wireless communications systems andmethods and, more specifically, relate to cellular wirelesscommunications systems and to techniques for a mobile station totransition from one cell to another.

BACKGROUND

The following abbreviations are herewith defined.

BSC Base Station Controller

BTS Base Transceiver Station

CN Core Network

CRS Cell Re-Selection

DL Down Link (to the MS)

EDGE Enhanced Data rate for Global Evolution

EGPRS Enhanced General Packet Radio Service

GERAN GSM/EDGE Radio Access Network

GGSN Gateway GPRS Support Node

GPRS General Packet Radio Service

GMM GPRS Mobility Management

GSM Global System for Mobile Communications

GSN GPRS Support Node

HO Handover

LLC Logical Link Control

MAC Medium Access Control

MS Mobile Station

MSC Mobile Switching Center

PDP Packet Data Protocol

PDU Packet Data Unit

RLC Radio Link Control

RNC Radio Network Controller

SAPI Service Access Point Indicator

SGSN Serving GPRS Support Node

TBF Temporary Block Flow

TLLI Temporary Logical Link Identity

UL Uplink (from the MS)

UMTS Universal Mobile Telecommunications System

URA User (or UTRAN) Registration Area

UTRAN Universal Terrestrial Radio Access Network

Reference can also be made to 3GPP TR 21.905, V4.4.0 (2001-10), ThirdGeneration Partnership Project; Technical Specification Group Servicesand System Aspects; Vocabulary for 3GPP Specifications (Release 4), aswell as to ETSI TR 101 748, V8.0.0 (2000-05), Digital cellulartelecommunications system (Phase 2+); Abbreviations and acronyms (GSM01.04 version 8.0.0 release 1999).

In general, when the MS (Mobile Station) changes from one cell toanother in the GPRS (General Packet Radio Service) system any ongoingTBFs in the old cell are terminated and the new cell is entered. Thecell change decision can be made by the MS or by the wireless network.In the case where the network makes the cell change decision, thenetwork sends a Packet Cell Change Order message to the MS. The MSleaves the old cell and enters the new cell almost as if the MS haditself made the cell change decision.

In GPRS there is no handover as in the GSM system, meaning that theradio connections (TBFs) are not maintained during the cell change. Whenthe MS enters the new cell any ongoing TBFs in the old cell are releasedand re-established in the new cell. A handover procedure in which radioresources are pre-allocated in the new cell is not currently defined inthe GPRS specification.

When the GPRS MS is operating in a GMM (GPRS Mobility Management) READYstate, and when the MS enters the new cell, the MS is expected to sendan LLC PDU (Logical Link Control Packet Data Unit) to the SGSN (ServingGPRS Support Node). Based on the LLC PDU the SGSN is able to determinein which cell the MS is located. As such, the SGSN is not required toinitiate a Paging procedure when sending LLC PDUs to the MS.

In the GPRS system, when a MS operating in the GMM READY state changesto a new cell (either MS initiated or network controlled) that isassociated with the same routing area as the previous cell, thefollowing process is executed:

(i) the MS determines that it will change to the new cell;

(ii) the MS terminates all TBFs (Temporary Block Flows) in the previouscell, meaning that an ongoing data transfer is terminated abnormally (aTBF is a unidirectional radio connection between MS and the network,where there may be an UL (Uplink) and/or a DL (Downlink) TBF establishedat any given time);

(iii) the MS enters the new cell;

(iv) the GMM or LLC of the MS (depending on the implementation) requeststhe LLC to send a LLC PDU to the network;

(v) the LLC of the MS sends the LLC PDU to the RLC/MAC of the MS;

(vi) when the RLC/MAC of the MS has obtained the parameters related topacket access from a System Information message being broadcast in thenew cell, or has obtained these parameters via some other means (such asfrom the previous cell), the RLC/MAC of the MS initiates an UL TBFestablishment procedure;

(vii) when the UL TBF is established, the RLC/MAC sends the LLC PDU tothe network; and

(viii) the SGSN determines from the received LLC PDU the new location ofthe MS.

A publication entitled Digital Cellular Telecommunications System (Phase2+); General Packet Radio Service (GPRS); Mobile Station (MS)—BaseStation System (BSS) interface; Radio Link Control/Medium Access Control(RLC/MAC) protocol; (GSM 04.60 version 6.8.0 Release 1997) requires thatthe received (and segmented) LLC PDUs be put into RLC data blocks in thesame order as they are received from higher layers. This means that ifthere was an ongoing data transfer in the previous cell, the RLC of theMS may have several untransmitted LLC PDUs in its transmit buffer thatare to be transmitted to the network in the new cell. Theabove-mentioned cell change LLC PDU that was initiated by the GMM isthus placed in the last available entry of the transmit queue (i.e.,behind any untransmitted LLC PDUs). Before the SGSN receives the firstLLC PDU from the MS via the new cell, the SGSN sends all DL LLC PDUs tothe previous cell. If the LLC is operating in an unacknowledged (UNACK)mode, the DL LLC PDUs destined to be transmitted to the previous cellare discarded because the network can not contact the MS via theprevious cell. If the LLC is operating in an acknowledge (ACK) mode,those DL LLC PDUs destined to be transmitted to the previous cell mustbe retransmitted to the new cell, which takes time and unnecessarilywastes network resources.

Two examples are now provided to further clarify the current state ofthe prior art.

Example 1, ACK RLC mode

Assume that the RLC of the MS has one 1500 octet LLC PDU in its transmitbuffer when the MS changes from the previous cell to the new cell. InGPRS the radio resources may be shared between several MSs. If the MS isrequired to share TSs (time slots) that are assigned to its UL TBF withother MSs, the MS may not receive permission to send in a timely manner,and it may require a significant amount of time to transmit the LLC PDU.Furthermore, if some RLC data blocks are lost they must beretransmitted, which requires even more time. As a result, the SGSN maytransmit a large number of DL LLC PDUs to the previous cell before theSGSN learns of the new cell location of the MS.

Example 2, UNACK RLC mode

Assume as in example 1 that the RLC of the MS has one 1500 octet LLC PDUin its transmit buffer when the MS changes from the previous cell to thenew cell, and is also required to share radio resources. In the UNACKcase if some RLC data blocks are lost, the RLC on the network side setszero octets into the LLC PDU to replace the missing data octets. If theLLC in the SGSN calculates a CRC for the LLC PDUs, one missing RLC datablock means that the CRC calculation fails. Since it takes some tens ofRLC data blocks (depending on the channel coding scheme) to transmit one1500 LLC PDU, the probability of one block going missing for whateverreason is increased. If the LLC PDU CRC calculation fails in the SGSN,the LLC in the SGSN discards the LLC PDU and the SGSN does not updatethe new cell location of the MS.

The presence of missing user data packets can result in detrimental sideeffects for the user, as MS applications that rely on receiving the userdata packets can malfunction, or even cease to function.

As can be appreciated, there are significant problems inherent in theprior art approach to the MS changing cells in the GPRS.

SUMMARY OF THE PREFERRED EMBODIMENTS

The foregoing and other problems are overcome, and other advantages arerealized, in accordance with the presently preferred embodiments ofthese teachings.

Disclosed is a method for quickly notifying the SGSN of a change fromone cell to another by the MS. In accordance with this mobile stationexecuted method, upon changing from a current cell to a new cell in awireless packet data network, the mobile station enters the new cell;generates a cell change packet data unit (PDU) message for informing thenetwork of the location of the mobile station in the new cell; buffersthe cell change PDU message into a PDU transmit queue before anybuffered PDUs that were present before the mobile station entered thenew cell; and transmits the buffered cell change PDU before any of thebuffered PDUs that were present before the mobile station entered thenew cell. The step of transmitting includes a preliminary step ofrequesting an uplink resource, preferably a Temporary Block Flow (TBF),for transmitting the cell change PDU. The wireless packet data network,in response to receiving the cell change PDU, transmits downlink PDUsfor the mobile station into the new cell.

In the presently preferred embodiment the generated cell change PDU istransmitted only if a first PDU in the transmit queue exceeds apredetermined length, otherwise the cell change PDU is discarded and thefirst PDU in the transmit queue is transmitted instead.

In the presently preferred embodiment the wireless packet data networkis a General Packet Radio Service (GPRS) network, the PDUs are LogicalLink Control (LLC) PDUs, and the cell change LLC PDU has a length thatfits within one Radio Link Control (RLC) data block. In this case thestep of generating employs a LLC unit that uses a Service Access PointIndicator (SAPI) of a GPRS Mobility Management (GMM) unit to form anempty GMM PDU, and a mobile station location update procedure is thentriggered by the Serving GPRS Support Node (SGSN) when the GMM PDU isreceived. Also in this case a Radio Link Control/Medium Access Control(RLC/MAC) unit initiates an uplink TBF in the new cell, and indicates toa RLC/MAC of the network if an ACK or an UNACK RLC mode is to be usedwhen transmitting the cell change PDU. The RLC/MAC unit of the mobilestation selects either the ACK or the UNACK RLC mode based on the RLCmode of a next queued LLC PDU in the transmit queue.

The above-described mechanism is presently preferred, since if the RLCmode changes during a TBF, the ongoing TBF is released and another TBFis established with the new RLC mode. If a cell change LLC PDU and thenext LLC PDU in the RLC buffer use the same RLC mode, they can betransmitted within the same TBF.

In accordance with the teachings of this invention, when the MS changesto the new cell the SGSN is enabled to more rapidly determine the newcell location of the MS, and thus DL LLC PDUs being sent to the MS canbe directed more rapidly to the correct (new) cell. The result is fewermissing LLC PDUs, more efficient usage of network resources and betterservice for the user.

In accordance with a further embodiment of this invention a method isdisclosed for informing the wireless network SGSN that the MS has made acell change. This method includes changing from a first cell to a secondcell with the MS and, prior to the SGSN receiving a communication fromthe MS, notifying the SGSN of the MS cell change. The communication maybe at least one of a Packet Data Unit (PDU) and a message.

In one embodiment the step of notifying includes steps of: (a) inresponse to the MS making access in the second cell, sending a ChannelRequest that indicates a Cell Update operation; (b) establishing anuplink (UL) Temporary Block Flow (TBF) for transferring Logical LinkControl (LLC) Packet Data Units (PDUs) from the MS to the network; (c)in response to the network receiving an unknown Temporary Logical LinkIdentifier (TLLI) from the MS, sending a message to the SGSN; and (d)based on the message, determining with the SGSN the that the MS islocated in the second cell. The TLLI may be received in a PacketResource Request message, in the case of a two phase access, or in afirst Radio Link Control (RLC) data block, in the case of a one phaseaccess.

In other embodiments the step of notifying occurs in response to the MSbeing assigned a TDMA frame number of when to make the cell change, oroccurs in response to the network receiving a Radio Link Control/MediumAccess Control (RLC/MAC) message from the MS, or occurs in general inresponse to the network receiving a TLLI from the MS.

These teachings also provide a method and an apparatus for organizingPDUs into a transmit queue. In this embodiment the method includespassing a PDU to a Radio Link Control (RLC) unit, the PDU having a flagfor indicating a priority of the PDU relative to other PDUs; storing thePDU into the transmit queue in accordance with the indicated priority;and transmitting the stored PDU to a radio channel before any storedPDUs having a lower priority. For the case where the RLC unit isassociated with the mobile station, the PDU is a cell change PDU and thecell change PDU is assigned a highest priority.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of these teachings are made more evidentin the following Detailed Description of the Preferred Embodiments, whenread in conjunction with the attached Drawing Figures, wherein:

FIG. 1 is a simplified block diagram of an embodiment of a wirelesscommunications system that is suitable for practicing this invention;

FIG. 2 is a logic flow diagram that is descriptive of a first method inaccordance with this invention; and

FIG. 3 is a logic flow diagram that is descriptive of a second method inaccordance with this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is illustrated a simplified blockdiagram of an embodiment of a wireless communications system 5 that issuitable for practicing this invention. The wireless communicationssystem 5 includes at least one mobile station (MS) 100. FIG. 1 alsoshows an exemplary network operator having, for example, a Serving GPRSSupport Node (SGSN) 30 for connecting to a telecommunications network,such as a Public Packet Data Network or PDN, via a Gateway GPRS SupportNode (GGSN) 32, at least one base station controller (BSC) 40, and aplurality of base transceiver stations (BTS) 50 that transmit in aforward or downlink direction both physical and logical channels to themobile station 100 in accordance with a predetermined air interfacestandard. A reverse or uplink communication path also exists from themobile station 100 to the network operator, which conveys mobileoriginated access requests and traffic. Each BTS 50 supports a cell,such as a serving cell that is currently serving the MS 100, and atleast one neighbor cell, which can be a new cell that the MS 100 entersfrom the servicing cell (which then becomes the previous cell).

The air interface standard can conform to any suitable standard orprotocol, and may enable both voice and data traffic, such as datatraffic enabling Internet 70 access and web page downloads. In thepresently preferred embodiment of this invention the air interfacestandard is a Time Division Multiple Access (TDMA) air interface thatsupports a GSM or an advanced GSM protocol and air interface, althoughthese teachings are not intended to be limited to TDMA or to GSM orGSM-related wireless systems.

The network operator may also include a suitable type of Message Center(MC) 60 that receives and forwards messages for the mobile stations 100.Other types of massaging service may include Supplementary Data Servicesand possibly Multimedia Messaging Service (MMS), wherein image messages,video messages, audio messages, text messages, executables and the like,and combination thereof, can be transferred between the network and themobile station 100.

The mobile station 100 typically includes a microcontrol unit (MCU) 120having an output coupled to an input of a display 140 and an inputcoupled to an output of a keyboard or keypad 160. The mobile station 100may be a handheld radiotelephone, such as a cellular telephone or apersonal communicator. The mobile station 100 could also be containedwithin a card or module that is connected during use to another device.For example, the mobile station 10 could be contained within a PCMCIA orsimilar type of card or module that is installed during use within aportable data processor, such as a laptop or notebook computer, or evena computer that is wearable by the user.

The MCU 120 is assumed to include or be coupled to some type of a memory130, including a read-only memory (ROM) for strong an operating program,as well as a random access memory (RAM) for temporarily storing requireddata, scratchpad memory, received packet data, packet data to betransmitted, and the like. A transmit buffer (XMIT BUFFER) 130A isassumed to be contained in the memory 130. A separate, removable SIM(not shown) can be provided as well, the SIM storing, for example, apreferred Public Land Mobile Network (PLMN) list and othersubscriber-related information. The ROM is assumed, for the purposes ofthis invention, to store a program enabling the MCU 120 to execute thesoftware routines, layers and protocols required to implement themethods in accordance with these teachings. As such, and forconvenience, associated with the MCU 120 is shown a RLC/MAC unit 120A, aGMM unit 120B and a LLC unit 120C. While shown as functional blocks, inpractice each of these is implemented by software instructions that areexecuted by the MCU 120.

It should be noted that the wireless network 10, such as the SGSN 30,has associated therewith a RLC/MAC unit 30C, a GMM unit 30B and a LLCunit 30A. While shown as functional blocks, in practice each of these isalso implemented by software instructions that are executed a dataprocessor that is resident at the network operator 10. According to thecurrent specification, the network RLC/MAC may be located in the BTS 50,the BSC 40, or in the SGSN 30.

The ROM of the MS 100 also typically stores a program that provides asuitable user interface (UI), via display 140 and keypad 160.

Although not shown, a microphone and speaker are typically provided forenabling the user to conduct voice calls in a conventional manner.

The mobile station 100 also contains a wireless section that includes adigital signal processor (DSP) 180, or equivalent high speed processoror logic, as well as a wireless transceiver that includes a transmitter200 and a receiver 220, both of which are coupled to an antenna 240 forcommunication with the network operator. At least one local oscillator(LO) 260, such as a frequency synthesizer, is provided for tuning thetransceiver. Data, such as digitized voice and packet data, istransmitted and received through the antenna 240.

Referring now as well to FIG. 2, the following method is employed, inaccordance with this invention, to improve the cell change procedurewhen the MS 100 has data to transmit to the network 10.

At Step 2A it is assumed that the RLC/MAC unit 120A of MS 100 has one ormore LLC PDU(s) in the transmit buffer 130A when the change from thecurrent cell to the new cell takes place. The GMM unit 120B (or the LLCunit 120C) requests the LLC unit 120C to transmit the LLC PDU in orderto notify the SGSN 30 of the cell change.

At Step 2B the LLC unit 120C composes a short LLC PDU and sends it tothe RLC/MAC unit 120A. Preferably the LLC PDU is short enough to fitwithin one RLC data block, as will be discussed in further detail below.

At Step 2C the RLC/MAC unit 120A detects that the received LLC PDU is acell change LLC PDU (e.g., based on a flag or other information receivedfrom the LLC unit 120C with the LLC PDU). In response, the cell changeLLC PDU is placed at the head of the LLC PDU transmit queue (i.e.,before any buffered LLC PDUs in the transmit buffer 130A). As an option,if the first LLC PDU in the transmit buffer 130A is short enough (e.g.,less than about 50 octets), the RLC/MAC 120A may discard the cell changeLLC PDU sent by the GMM unit 120B in order not to transfer unnecessaryoctets to the network.

Further in this regard, it is noted that when the cell change takesplace, the MS 100 transmits the LLC PDU to the SGSN 30 and, based on theLLC PDU, the SGSN 30 determines the new location of the MS 100. The LLCPDU may be any valid LLC PDU such as, but not limited to, user data, GMMsignalling, or an LLC ACK. In this case if the head of the MS 100RLC/MAC transmit queue 130A happens to contain, for example, a LLC ACKPDU (having a length of, for example, six octets), this LLC PDU may betransmitted to the network.

It is also within the scope of these teachings to provide a generalmechanism to prioritize the contents of the transmit queue 130A. Forexample, a PDU such as a LLC PDU (in (E)GPRS) or a 3G PDP when passed tothe RLC can contain a flag that is used when buffering the PDU. In oneembodiment, the flag can comprise just on bit that when set causes thePDU to be buffered so that it becomes the next PDU to be transmitted(i.e., it is put at the head of the transmit queue in buffer memory130A.) In this case the flag can be set for the cell change PDU causingit to be transmitted before any other buffered PDUs.

In another embodiment the flag can comprise more than one bit, and thusspecifies an internal priority (IP). For example, a Data PDU can have aflag indicating an IP of four, while a GMM Cell Update PDU may have anIP equal to one. The RLC then organizes the PDUs in the transmit buffer130A according to their respective priorities such that the higherpriority PDUs are transmitted before the lower priority PDUs.

EXAMPLE

Current queue: [ip1 packet1] [ip1 packet2] [ip2 packet 3] [ip4 packet4]. In this case packet1 is the first to be transmitted to the network.The RLC next receives a new PDU (packet5) from the upper layerscontaining an internal priority=1. This results in Current queue: [ip1packet1] [ip1 packet2] [ip1 packet5] [ip2 packet 3] [ip4 packet 4]. TheRLC then receives new PDU (packet6) from the upper layers containing aninternal priority=3. This results in Current queue: [ip1 packet1] [ip1packet2] [ip1 packet5] [ip2 packet 3] [ip3 packet 6] [ip4 packet 4]. Itshould be noted that this procedure is not limited for execution by thecontroller 120 of the mobile station 100, but could be executed as wellat the network operator 10.

In accordance with this aspect of the invention, and having now thusmore advantageously staged the cell change LLC PDU into the transmitbuffer queue 130A, the following steps may be similar to those executedin the prior art case discussed above. For example, at Step 2D, when theRLC/MAC 120A of the MS 100 has obtained the parameters related to packetaccess from a System Information message being broadcast in the newcell, or has obtained these parameters via some other means (such asfrom the previous cell), the RLC/MAC 120A of the MS 100 initiates an ULTBF establishment procedure. At Step 2E, when the UL TBF is established,the RLC/MAC 120A sends the LLC PDU to the network 10. However, inaccordance with this invention the first LLC PDU to be sent in the newcell is the cell change LLC PDU that was inserted into the head of thetransmit buffer queue by the RLC/MAC unit 120A. At Step 2F the SGSN 30learns from the received cell change LLC PDU the new location of the MS100, and DL PDUs are redirected accordingly.

It is noted that it is advantageous if the cell update LLC PDU does notuse the same LLC SAPI (Service Access Point Indicator) as the normaldata LLC PDUs so that the LLC PDU numbering does not become confused.When the SGSN 30 receives LLC PDUs in the wrong order (as indicated bythe SAPI), and if the SGSN LLC 30A is operating in the ACK mode, the LLC30B in the SGSN 30 would send an ACK or a SACK PDU to the MS 100 andthus waste network resources. It is preferred that the LLC unit 120C useSAPI of the GMM unit 120B and form an empty GMM PDU. In this case theLLC PDU triggers the MS 100 location update procedure when it isreceived by the SGSN 30, and the receiving LLC is not confused.

It is further noted that when the RLC/MAC unit 120A initiates the UL TBFestablishment in the new cell, the RLC/MAC unit 120A indicates to thenetwork's RLC/MAC 30C if the ACK or the UNACK RLC mode is to be used. Inthis invention the RLC/MAC unit 120A of the MS 100 may always use theACK RLC mode for the cell change LLC PDU in order to ensure that thecell change PDU is received by the network 10. However, in that the cellchange LLC PDU is preferably short enough (e.g., less than about 20octets) so as to fit into one RLC data block, the RLC/MAC 120A isenabled to determine the RLC mode of the next queued LLC PDU in thetransmit buffer 130A, and may thus use the same mode for the cell changeRLC mode. This is advantageous, as otherwise a new UL TBF would need tobe established for the next LLC PDU, as one UL TBF may carry RLC datablocks only in one RLC mode (i.e., either ACK or UNACK). By making theRLC mode of the UL cell change LLC PDU the same as the RLC mode of nextqueued LLC PDU, the establishment of another UL TBF is avoided and timeand network resources are saved.

Further in accordance with these teachings, and referring to FIG. 3,another technique for rapidly informing the SGSN 30 of the MS 100 cellchange is as follows:

(Step 3A) The MS 100 makes access in the new cell with a (Packet)Channel Request. In the access type field the MS indicates a Cell Updateoperation.

(Step 3B) An UL TBF is established for transferring LLC PDUs from the MS100 to the network 10.

(Step 3C) When the network receives a temporary MS 100 identity(Temporary Logical Link Identifier (TLLI)) either in a Packet ResourceRequest message, in the case of a two phase access, or in the first RLCdata blocks, in the case of a one phase access, the network 10 sends amessage to the SGSN 30. Based on the message the SGSN 30 is enabled todetermine the new cell location of the MS 100.

The use of one phase and two phase accesses are well known and basicprocedures in (E)GPRS. For example, reference can be made to GSM 04.60(e.g., versions 6.X.Y or 8. X.Y), Section 7. In the case where the MS100 makes a one phase access the MS 100 is not able to accuratelydetermine what type of data it is about to transmit. (the RLC defaultsto the ACK mode). In the case of the two phase access, the networkallocates first only one (or two in the case of EGPRS) sendingpermissions for the MS 100. In the sending permission the MS 100transmits a Packet Resource Request message, wherein the MS 100 canaccurately define what kind of data the MS 100 is about to transmit(e.g., RLC mode ack/nack, throughput and so forth).

The foregoing technique shown in FIG. 3 is an alternative method forquickly informing the SGSN 30 of the MS 100 cell change. The RLC/MAC 30Cof the network may check the TLLI type when deciding when to send thecell change message to the SGSN 30. For example, the RLC data blockreceived with a local TLLI does not generate a cell change message tothe SGSN 30, but the RLC data block received with a random or foreign orotherwise unknown TLLI generates the cell change message to the SGSN 30.A random/foreign TLLI is considered herein to be one that has not (yet)been allocated by the SGSN 30, and thus can not be used in a normal datatransfer.

Furthermore, the access type may also be considered. For example, for acase where the MS 100 indicates a cell change as a reason forestablishing an UL TBF, the SGSN 30 may be notified when receiving, forexample, the TLLI from the MS 100.

In general, and in accordance with this aspect of the invention, theSGSN 30 is informed of the new location of the MS 100 before the SGSN 30receives a PDU/message from the MS 100. Furthermore, notifying the SGSN30 upon reception of the TLLI, as described above, is but one embodimentfor performing the SGSN 30 notification function. For example, inanother embodiment the radio part of the network (e.g. network elementscontaining the RLC/MAC 30C) synchronizes the MS cell change in the caseof a network controlled cell change. That is, the MS 100 is given, forexample, a TDMA frame number in the old cell of when to perform the cellchange, and the SGSN 30 may then be notified of when the cell changetakes place. In this case the SGSN 30 may be notified of the newlocation of the MS 100 even before the MS 100 begins communicating tothe network, or it may be notified after the network has received sometype of confirmation that the MS 100 is within the new cell.

For example, the SGSN 30 may be informed of the MS cell change eitherwhen the cell change takes place, or when the network receives a RLC/MACmessage from the MS 100, or a TLLI from the MS 100. These variousembodiments may be especially useful for performing cell-to-cell MS 100handovers.

While described in the context of various messages and GPRS-specificfunctions, those having skill in the art should appreciate that theteachings of this invention are not intended to be limited to only thepresently preferred embodiments. The foregoing method is applicable toany packet based network that allows user mobility. The disclosed methodclearly improves the cell change procedure, as well as conservingnetwork resources and speeding up the user data transmission. While thedisclosed method is especially applicable for GPRS, EGPRS and GERAN, itis not limited for use in only these network types.

1-28. (canceled)
 29. A method, comprising: entering a new cell;generating a cell change logical link control (“LLC”) packet data unit(“PDU”) for informing a network of a location of a mobile station in anew cell; buffering the cell change LLC PDU into a LLC PDU transmitqueue such that the cell change LLC PDU is selected for transmissionprior to any other buffered packet data units that are present in theLLC PDU transmit queue when the cell change LLC PDU is buffered; andtransmitting the buffered cell change LLC PDU before any of the otherbuffered packet data units that are present in the LLC PDU transmitqueue when the cell change LLC PDU is buffered.
 30. A method as in claim29, further comprising requesting an uplink resource for transmittingprior to transmitting the cell change LLC PDU.
 31. A method as in claim29, further comprising requesting an uplink temporary block flow fortransmitting prior to transmitting the cell change LLC PDU.
 32. A methodas in claim 29, wherein the generated cell change LLC PDU is transmittedonly if a first packet data unit in the transmit queue exceeds apredetermined length, otherwise the cell change LLC PDU is discarded andthe first packet data unit in the transmit queue is transmitted instead.33. A method as in claim 29, where the cell change LLC PDU has a lengththat fits within one radio link control (“RLC”) data block.
 34. A methodas in claim 33, wherein the generating operates a logical link controlunit to use a service access point of a general purpose radio service(“GPRS”) mobility management unit to form an empty GPRS mobilitymanagement packet data unit, and where a mobile station location updateprocedure is triggered by a serving GPRS support node when the GPRSmobility management packet data unit is received.
 35. A method as inclaim 33, wherein a radio link control/medium access control (“RLC/MAC”)unit initiates an uplink temporary block flow in the new cell, andindicates to a RLC/MAC of the network if an ACK or an UNACK radio linkcontrol mode is to be used when transmitting the cell change LLC PDU.36. A method as in claim 35, wherein the RLC/MAC unit of the mobilestation selects either the ACK or the UNACK RLC mode based on the UNACKRLC mode of a next queued packet data unit in the LLC PDU transmitqueue.
 37. A method as in claim 29, wherein the generating includessetting a priority level of the cell change LLC PDU such that bufferingthe cell change LLC PDU into the LLC PDU transmit queue causes the cellchange LLC PDU to be transmitted before any lower priority packet dataunits.
 38. An apparatus comprising: a packet data buffer; a controllerthat is responsive to changing a location from a previous cell to a newcell in a wireless packet data network, and for generating a cell changelogical link control (“LLC”) packet data unit (“PDU”) for informing thewireless packet data network of the presence of the apparatus in the newcell, and for buffering the cell change LLC PDU into the packet databuffer such that it is selected. for transmission prior to any otherbuffered packet data units that are present in the packet data bufferwhen the cell change LLC PDU is buffered a transmitter for transmittingthe buffered cell change LLC PDU prior to the other buffered packet dataunits that are present in the packet data buffer when the cell changeLLC PDU is buffered, for informing the wireless packet data network ofthe cell in which the apparatus is currently located so that packet dataintended for the apparatus is not transmitted into the previous cell bythe wireless packet data network.
 39. An apparatus as in claim 38wherein the controller, prior to operating said transmitter fortransmitting the buffered cell change LLC PDU, requests an uplinkresource for transmitting the cell change LLC PDU.
 40. An apparatus asin claim 38 wherein the controller, prior to operating said transmitterfor transmitting the buffered cell change LLC PDU, requests an uplinktemporary block flow for transmitting the cell change LLC PDU.
 41. Anapparatus as in claim 38, wherein the generated cell change LLC PDU istransmitted only if a first packet data unit in the transmit bufferexceeds a predetermined length, otherwise the cell change LLC PDU isdiscarded and the first packet data unit in the packet data buffer istransmitted instead.
 42. An apparatus as in claim 38, where the cellchange LLC PDU has a length that fits within one RLC data block.
 43. Anapparatus as in claim 42, wherein said controller, when generating thecell change LLC PDU, operates a logical link control unit to use aservice access point indicator (“SAPI”) of a GPRS management unit toform an empty GPRS mobility management packet data unit, and where anapparatus location update procedure is triggered by a serving GPRSsupport node when the GPRS mobility management packet data unit isreceived.
 44. An apparatus as in claim 42, wherein said controlleroperates a RLC/MAC unit to initiate an uplink temporary block flow inthe new cell, and to indicate to a RLC/MAC of the network if an ACK oran UNACK radio link control mode is to be used when transmitting thecell change LLC PDU.
 45. An apparatus as in claim 44, wherein theRLC/MAC unit of the apparatus selects either the ACK or the UNACK RLCmode based on the RLC mode of a next queued logical link control packetdata unit in the packet data buffer.
 46. An apparatus as in claim 38,wherein controller sets a priority level of the cell change LLC PDU suchthat when buffering the cell change LLC PDU into the packet data bufferthe cell change LLC PDU is caused to be transmitted before any lowerpriority packet data units.
 47. A method comprising: passing, by amobile station, a cell change logical link control (“LLC”) packet dataunit (“PDU”) to a (“RLC”) unit for informing a network of a location ofthe mobile station in a new cell, the cell change LLC PDU having a flagfor indicating a priority of the LLC PDU relative to other packet dataunits; storing, in the mobile station, the cell change LLC PDU into alogical link control packet data unit transmit queue in accordance withthe indicated priority, wherein the cell change LLC PDU comprises anempty GPRS mobility management packet data unit to notify the network toupdate mobile station location information; and transmitting the storedcell change LLC PDU to a radio channel before any stored packet dataunits having a lower priority that are present in the transmit queuewhen the cell change LLC PDU is buffered into the transmit queue.
 48. Amethod as in claim 47, where the cell change LLC PDU is assigned ahighest priority.
 49. A non-transitory computer readable medium embodiedwith a computer program the execution of which in association with adevice cell change operation, in response to entering a new cell,performs operations of: generating a cell change logical link control(“LLC”) packet data unit (“PDU”) for informing a wireless network of thelocation of the device, wherein generating includes forming an emptyGPRS mobility management packet data unit to notify the network toupdate mobile station location information; and buffering the cellchange LLC PDU into a LLC PDU unit transmit queue such that it istransmitted to the network before any already buffered packet data unitsthat are present in the LLC PDU transmit queue when the cell change LLCPDU is buffered into the LLC PDU transmit queue; and transmitting thebuffered cell change LLC PDU before the buffered packet data units thatare present when the cell change LLC PDU is buffered into the LLC PDUtransmit queue.
 50. A non-transitory computer readable medium embodiedwith a computer program as in claim 49, further comprising requestingfrom the wireless network an uplink resource for transmitting prior totransmitting the cell change LLC PDU.
 51. A non-transitory computerreadable medium embodied with a computer program as in claim 49, furthercomprising requesting from the wireless network an uplink temporaryblock flow prior to transmitting the cell change LLC PDU.
 52. Anon-transitory computer readable medium embodied with a computer programas in claim 49, where the cell change LLC PDU has a length that fitswithin one radio link control (“RLC”) data block, and where thegenerating operation operates a logical link control unit to use aservice access point indicator (“SAPI”) of a general packet radioservice (“GPRS”) mobility management unit to form an empty GPRS mobilitymanagement packet data unit, and where a device location updateprocedure is triggered by a serving GPRS support node when the GPRSmobility management packet data unit is received.
 53. A non-transitorycomputer readable medium embodied with a computer program as in claim49, where the cell change LLC PDU has a length that fits within oneradio link control data block, and where a RLC/MAC unit initiates anuplink temporary block flow in the new cell.
 54. A non-transitorycomputer readable medium embodied with a computer program as in claim53, where a device RLC/MAC unit selects either the ACK or the UNACK RLCmode based on the RLC mode of a next queued logical link control packetdata unit in the transmit queue.
 55. A non-transitory computer readablemedium embodied with a computer program as in claim 49, where thegenerating operation comprises setting a priority level of the cellchange LLC PDU such that buffering the cell change LLC PDU into thepacket data unit transmit queue causes the cell change LLC PDU to betransmitted before any lower priority packet data units.
 56. A device,comprising: means, responsive to entering a new cell, for generating acell change logical link control (“LLC”) packet data unit (“PDU”) forinforming a wireless network of a location of the device, the means forgenerating being arranged to form an empty general packet radio servicemobility (“GPRS”) management packet data unit to notify the network toupdate mobile station location information; and means for buffering thecell change LLC PDU into a logical link control packet data unittransmit queue such that it is transmitted to the wireless networkbefore any already buffered packet data units that were present in thetransmit queue before buffering the cell change LLC PDU in the transmitqueue; and means for transmitting the buffered cell change LLC PDUbefore any of the buffered packet data units that were present in thetransmit queue before buffering the cell change LLC PDU in the transmitqueue.
 57. A device as in claim 56, further comprising means forrequesting from the wireless network an uplink resource prior totransmitting the cell change LLC PDU.
 58. A device as in claim 56,further comprising means for requesting from the wireless network anuplink temporary block flow prior to transmitting the cell change LLCPDU.
 59. A device as in claim 56, where the cell change LLC PDU has alength that fits within one (“RLC”) data block, and where the generatingmeans operates a logical link control unit to use a service access pointindicator (“SAPI”) of a general packet radio service (“GPRS”) mobilitymanagement unit to form an empty GPRS mobility management packet dataunit, and where a device location update procedure is triggered by aserving GPRS support node when the GPRS mobility management packet dataunit is received.
 60. A device as in claim 56, where the cell change LLCPDU has a length that fits within one radio link control data block, andwhere a (“RLC/MAC”) unit initiates an uplink temporary block flow in thenew cell.
 61. A device as in claim 60, where a device RLC/MAC unitselects either the ACK or the UNACK RLC mode based on the RLC mode of anext queued LLC PDU in the transmit queue.
 62. A device as in claim 56,where the generating means sets a priority level of the cell change LLCPDU such that buffering the cell change LLC PDU into the LLC PDUtransmit queue causes the cell change LLC PDU to be transmitted beforeany lower priority packet data units that were present in the LLC PDUtransmit queue before buffering the cell change LLC PDU in the LLC PDUtransmit queue.